1. Field of the Invention
The present invention relates to a die for extruding elongate articles made of a metal such as aluminum and having longitudinal orifices.
2. Description of the Prior Art
An example of the prior art dies 71 is shown in FIG. 10, which has been used to extrude elongate articles `E` of aluminum or the like metal and each having a longitudinal orifice `h` as shown in FIG. 9A, 9B or 9C.
This die 71 of the port-hole type is an die assembly consisting of a male die 72 and a female die 73 combined therewith. The male die 72 has an orifice former 74 needle-shaped and protruding forwards. This orifice former 74 integral with the male die is to be located within a forming hole 75 of the female die 73 combined with the male die 72. The extrudate `E` extruded through this die 71 will have an outer periphery corresponding to the inner periphery of the forming hole 75 of the female die 73, with the orifice former 74 thereby producing the longitudinal orifice `h` extending through the extrudate.
However, it has not been easy even for the electrospark machining to make such an orifice former 74 integral with the male die 72 in those prior art dies, especially where said former 74 must be of high precision in shape and dimension.
It has been almost impossible to prepare a highly precise orifice former 74 that could form an extremely thin orifice `h` having a diameter for example of 3 mm or less.
Further, it has been another problem that a male die 72 must be replaced entirely with a new one even when only the orifice former 74 would be worn.